1. Field of the Invention
The present invention relates to a structure of an opening section of a fuel tank made of a thermoplastic synthetic resin.
2. Description of Related Art
Conventionally, fuel tanks made of metals have been used as fuel tanks for use in motor vehicles, etc. but, recently, fuel tanks made of thermoplastic synthetic resins have been frequently used, because they can effect lightweight vehicle bodies, no rust is generated therein, and they can be readily formed into desired configurations.
In many cases, the fuel tanks made of thermoplastic synthetic resins have been manufactured by the blow molding method, because tubular bodies can be readily formed. With the blow molding method, a parison of a molten thermoplastic synthetic resin formed into a cylindrical configuration is extruded from the upper side of a mold, and air is blown into the parison while holding the parison with the mold, thereby manufacturing fuel tanks for use in motor vehicles.
Such a fuel tank has an opening section for removing or putting tank parts from or in an interior of the fuel tank. The opening section of the fuel tank is formed integrally with a tank main body upon forming the tank main body by the blow molding method.
Alternatively, the fuel tank have been manufactured by forming an upper tank member and a lower tank member separately by the injection molding method, and welding them together. In this case, an opening section is also provided for removing or putting a fuel pump, etc. from or in the fuel tank.
In order to open and close this opening section, a camlock type opening structure has been used (See Published Japanese patent application No. 2005-248954 and Japanese translation of PCT International application No. 2006-526542, for example.) As shown in FIG. 1, an engaging member 10 is provided in an opening section 12 of a tank. The engaging member 10 has a plurality of hook-shaped claw parts 14. A tank cap 16 is held with the engaging member 10 and an attaching member 18 while engaging the claw parts 14 in holes 20 provided in the attaching member 18. As a result, the tank cap 16 is attached to the opening section 12.
Alternatively, as shown in FIGS. 2, 3 and 4, a plurality of holes 22 are provided in an engaging member 24 whereas a plurality of claw parts 26 are provided in an attaching member 28, and a tank cap 30 is attached to an opening section of a fuel tank by engaging the claw parts 26 in the holes 22. In order to attach the tank cap 30 to the opening section of the fuel tank, the positioning of the tank cap 30 is needed. To this end, positioning projections 32 are provided in the tank cap 30, and the positioning projections 32 are inserted in positioning holes 34 provided in the engaging member 24. And the claw parts 26 of the attaching member 28 are inserted in the holes 22 of the engaging member 24, and then the attaching member 28 is turned to hold the tank cap 30 in position.
When the tank cap 30 is detached, tip ends of an attaching and detaching tool (not shown) are inserted in access holes 36 provided along an outer periphery of the attaching member 28, and the attaching and detaching tool and the attaching member 28 are turned together to detach the attaching member 28 and the tank cap 30.
At this time, the access holes 36 may be overlapped with the positioning projections 32, and consequently, the positioning projections 32 may be damaged.